The present invention relates generally to the treatment of bones and more particularly to the treatment of the vertebral bodies found in the human spine.
The human spine consists of a complex set of interrelated anatomic elements including a set of bones called vertebral bodies. Intervertebral discs separate most vertebral bodies. These discs includes a xe2x80x9cspongyxe2x80x9d nucleus pulpous surrounded by an annulus fibrosis xe2x80x9cmembranexe2x80x9d. The annulus fibrosis connects the opposed endplates of adjacent vertebral bodies. All of these structures together with muscles act to provide motion, stability and protection for the spine. When healthy, these structures effectively protect the spinal cord and allow for normal motion.
However there are many disease states and aging processes that impact the patient. Osteoporosis and metastatic disease reduce the structural integrity of the vertebral bodies, predisposing them to fracture. Vertebral fractures can lead to loss of vertebral height which can exacerbate existing neurological condition or it can predispose the spine to other symptoms. Back pain often results from these conditions. Vertebroplasty is an effort to stabilize these fractures and to alleviate this source of pain.
Generally, fractures and loss of height if not treated results in a cascade of injury which is undesirable. For this reason various efforts have been directed at stabilizing and restoring the natural vertebral bodies of the back. Efforts have also been directed to replacing the vertebral bodies. condition or it can predispose the spine to other symptoms. Back pain often results from these conditions. Vertebroplasty is an effort to stabilize these fractures and to alleviate this source of pain.
Generally, fractures and loss of height if not treated results in a cascade of injury which is undesirable. For this reason various efforts have been directed at stabilizing and restoring the natural vertebral bodies of the back. Efforts have also been directed to replacing the vertebral bodies.
U.S. Pat. No. 5,108,404 to Scholten et al among others teaches a technique for height restoration that uses a bone cement product introduced into a cavity after a cavity has been made with an inflatable device. One problem with this system is the extravasation of bone cement to sensitive areas. Another problem is the difficulty of obtaining consistent control of height restoration with the Scholten system.
In contrast to the prior art, the present invention involves both a container device that is permanently implanted and a method of using the container to stabilize the vertebral body or to restore height to the vertebral body.
In one embodiment the container is porous to the bone filler material. In another embodiment the container is impermeable to the bone filler material. In each embodiment the container controls and regulates the delivery of bone filler material into the vertebral body.
In one embodiment the container is flexible and conformal to the cavity. In another embodiment the container has a fixed shape which conforms to the cavity shape when deployed.
In one embodiment of the method, the bone filler is injected until the cavity is completely filled stabilizing the vertebral body. In another embodiment of the method the bone filler is injected and displaces the endplates of the vertebral body xe2x80x9crestoring heightxe2x80x9d through a hydraulic jacking effect and stabilizing their vertebral body.
There are numerous bone filler materials which can be used to fill the container including bone cement and other materials. However it is a general property of the bone fillers that they must be injectable in a fluid state and that they harden.